The present invention relates to a system for conveniently providing load testing termination for an AC power source, e.g., generators or a static converters, having at least one battery and, more particularly, to a dummy load arrangement that is switchably connected to a selectable power signal generated for testing purposes by an AC uninterruptible power source system that includes a plurality of batteries.
AC power source finding application on large vessels or other large independently operated transport devices commonly include batteries that serve as secondary energy store devices and are commonly only used in the event of a failure in the primary AC power source. AC power sources, in these applications typically provide power excitation signals that are in the kilovolt-ampere (KVA) range and having a frequency of 60 H.sub.z or 400 H.sub.z while being configured in a three phase delta or wye arrangement. The AC power source commonly provides excitation to loads comprising equipment whose operation is of a critical nature and should not be disturbed by any power interruption of the AC power source itself. To accommodate such critical equipment, the primary AC power sources are arranged with batteries serving as a back-up excitation source, so as to provide for commonly termed uninterruptible power source (UPS) systems.
The batteries in these UPS systems are commonly connected to battery chargers, either internal or external to the UPS system, that include a d.c. power supply which is used to charge the batteries in the standby mode of the UPS system. These batteries, along with the UPS system itself, are commonly tested during routine maintenance. During such maintenance, input power to the UPS system is removed and the UPS system is disconnected from its critical equipment. An alternate AC power source is then connected to the critical load until the UPS system is tested. The UPS system is then connected to the appropriate test equipment. If the batteries are found to be defective, or if the AC generating equipment is found to be defective, the UPS system is out of service and must be disconnected from its critical load that desires uninterrupted power.
Even if the batteries and the UPS AC power sources are not defective, the time required for such testing is relatively long due to the inconvenience of disconnecting and reconnecting relatively large power cables carrying the relatively heavy currents. Furthermore, damage may occur to the UPS system because of the heavy input current surges that are typically created when the input power is re-applied to the UPS system. These surges may very well damage semiconductor devices within the UPS system. It is desired that means be provided that allow for the UPS system, including its batteries, to be more conveniently tested and without the need of removing and reapplying input power to the UPS system.